Transmission system



Nov. 28, 1933. M. CLEMENT TRANSMISSION SYSTEM Filed Nov. 2. 1 2

3 av k 0.0% mw /n venior:

Patented Nov. 28, 1933 manner 1 TRANSMISSION. srs'rEM;

Iiewis=M."Clemcnt-', East Orange, 'NAJZ', assigno r to Western. Electric Company, Incorporated, New, Y ork-,. N; Y., a corporation of New York ApplicationNovemBer 2; 1920. Serial No. 421,25I V 42 claims '(crest-seas) v This invention, relates to signaling systems and more particularly to radio systems capableof being operated to transmit a variety of signals and also capable of-transmitting-eachspecies of 1 signal with: various degreesof power.

It is well, known that in, radiosignaling; there is an advantage in beinggable-tdchange-a transmitter quickly so as'to transmit a difierent form:

of signal. and likewise tobe able withaparticular 1 form! ofsignal to-change the radiated power.

This invention includes improved and. practical means for accomplishing either or both of these purposes. Many features. of the invention are also applicable to wire or wireless teledynamicsysr v 1 tems in which it isdesirableto changethe transmitted Wave form or the power, and certain fea-- tures are of. still more general application. I In, the specific embodiment of i the invention dis-.

closed-herein, provision is made for transmitting. 205 speech bymodulating the carrier-wavetobetrans mitted in accordance with speech waves; for transmitting modulated continuous wave telegraph signals by modulating the waves tobe transmitted with a low frequency in; accordance with a code; and for transmitting continuous wave code signals. By continuous wave signaling as usedherein is meant a method of signaling wherein waves of uniform amplitude and frequency are intermittently interrupted for the purpose of sig-l 30.. naling. I

In the specific embodiment of the invention, vacuum. tubes are provided in connection with means whereby each'kind of signal may be-transmitted with high. power oscillations derived from 35. a plurality of tubes; medium power oscillations I produced by the maximum output of one tube, or I low power oscillations produced by 'a single tube working at reduced capacity. Movement of a single control switch having a plurality of contact 40; blades to any one of several selected positions conditions the apparatus for transmitting the" I I rigid extension or armature 53,,lthe. various. con-,-

desired form of signal, whilemovement of another switch regulates the power. arrangement of circuits connected to'the contacts and bladesof these switches a desirable simplicity of circuit arrangement is produced and efiective operation is secured.

When modulated waves are to be transmitted.

one or more modulating tubes areenergized. tov

' produce modulation of the transmitted waves, j

while an amplifier is energized for the purpose of increasing the energy of the modulating wave. The invention accordingly includes switching means to connect these elements in circuit when By a unique N they are to be operative and; to; deenergize-anddisconnect them from the not; operative,- thereby. preventing loss oil power in: II I idle, elements or interferencewiththefunctioning I I of; the'activeparts of the circuit.

Among the othe objects of. the inyention are i.

to prevent. sparking whentheantenna switch is thrown from the ftransmit position; tov providesimpleandefiicient meansfor. reducing thepower" below that ordinarily generated byasing'llspace' discharge device; to provide arrangements where by the speech input circuitand the telegraph. key. circuit are alvvays'ready tobe operated. whenthe function. switch ismoved to. the proper, position; I I and toproyide means: wherebyithe oscillator cO iL-E stants. and the coupling of.- the oscillator to. 01195 (I antenna are automatically. cliangedlwhelllithfii power1 ischanged.v I 1 ther objects and ad antageous featmesfwill, be apparent to. those skilled, in theflartkafterfl aperusal of the following.descriptionfand the; appended; claims wherein; thevariousjnovel fea turesof the invention are-set forth,

The. accompanying drawing illustrates, (lia I grammatically 'a radio transmission system; em;- I

bodying the invention.

An. antenna 1 may be connected tol a receiM- ing circuit 2 or a transmittin'g circuit. 3 by'means v ofatransmitereceive contact .controllerfor relay 5. The receivingfcircuitT2 may befofjany' of] the well-known types. for example, one,employ-} I ingan electron tube detector, asshown' inLj 'UQ S, Patent No}. 1,173,079. to,Alexanderson, February I 22, 1916, An oscillatoriO,.jgenerates.the'waves' to be transmitted. Qontrolling the circuits Off the oscillator in: a manner hereinafter described! is an auxiliary power switch or circuit clofserffi controlled by anau'xili'ary powerv relay 7, which.

is in turn controlled by a, manually operated.

power switch 8. I

,In the preferred, form apparatus 6, carryingthe contacted 0, 6., 2,0.a'nd'22; i'sfa,

transmitting positionasillustrated; 'itbei'ng con- I r I trolled through local. or. remote control by the, relay 5. through the circ'uitsfi, the system is capable of operating in several ways in, accjgird 11 0 25 the anodes of tubes 21'.

ance with the positioning of the power switch 8 and the function switch 9. Relay. is of the type which, upon being energized, moves over to the opposite position, breaks its own circuit, 5 and takes no more current until again energized for reverse movement. The complete circuits for operating this relay 5 are not illustrated as they form no part of the invention herein claimed. It need merely be stated that this relay is indi- 10 cated in the transmit position with the anture of relay 5. When the armature of relay 5 moves to the right, the contacts 4 and '33 move to the right and vice versa.

Telephony-high power Owing to the action of the coil 17 in tending to maintain the sum of the plate currents constant, variation in impedance of the modulating tubes will cause modulation of the high frequency .Waves produced by the oscillator. This type of 'system is known in the art as the constant current modulation system.

The coil 19 andthe capacity24 in parallel, form the highfrequency plate circuit of the oscillator which extends from the anodes through =these elements in parallel and through the capacity 25 and ground to the filaments. The purpose of the capacity 24 is to adjust the oscillator, for maximum efficiency, the frequency being regulated by varying the reactances in the -antenna .circuit 3.

- The plate circuit of the amplifierAm is completed through the conductor 26 which includes a resistance 27 for reducing the voltage applied to the amplifier. The function switch 9 closes the oontacts'28, 29, so and 31.

The cathodes of the various tubes are grounded and have a return connection to the negative side of source Eb through the ground 32, contact 33 of the transmit-receive switch, the'blade lifcontacts 30 and 6D, conductor 34, a part of resistance 35, contact 15, blade 0, blade A, and contact13 to the negativeterminal of the source Eb. Resistance 35 is of a small value; its use is later; described. The cathodes of the various tubes are energized through a circuit which extends from ground through battery Ea, the switch 36, and the conductor 37 to the positive terminals of the cathodes ofthe tube 23, the right hand tube of the system V, and'the amplifier tube Am.

, The connection to the positive terminals of; the

other tubes, included in the oscillating system and the modulating system V, is through the conductor 55, switch blade D, contact 16, and conductor 56. 'The negative terminals of the vari- 0 o ls cathodes are grounded when the tubes are energized. Thegroundconnection of the nega-' U tive terminals of the modulator and amplifiertubes is through the conductor 38 to the contact 39which is connected to the contact 28 and the switch blade F.

tenna connected to the transmitting circuits. 1 The contacts 4 and 33 are moved by the armadiagrammatic and isjnot intendedto show the cult of tubes 21 is opened at the contact 6'.

The grid input circuit of the oscillator extends from the grids of tubes 21 to the contact 6 and the grid of tube 23 through the conductor 54' and contact 40 to the conductor 41, thence through coil 42 and capacity 43 to ground. The grids are thus connected to the parallel combination of resistances 44 and 45 whichtogether form a high resistance leak path for all the grids through the coil 46 anda portion of resistance 35 to ground through conductor 34, contacts 60 and 36 and switch blade H.

The coil 46 is included to make the leak path inductive and'is preferably a coil wound upon a small wooden orother non-magnetic core. This coil preferably has small distributed capacity. 7

The telephone circuit 10 is connected to the transformer 47 through the blade I and the contact 31. The secondary of transformer 47 is connected to the input circuit of the amplifier Am whose output circuit is connected by the transformer 48 to the input circuit of the modulating tube system V. I

Telephony-intermediate power For intermediate power the power switch 8 is moved to close the contacts 49, 50, 51 and 52. This acts to deenergize. the tubes 21 and all but one of the modulating tubes V in the following manner. Blade B in moving from contact 14 to contact 50 causes an impulse of currentthrough the auxiliary power relay '7. The armature 53 is thereby thrown to the left and the contacts 46, a 6, 22 and 20, which are controlled by the armature'53 are also thrown to the left.

As soon as the auxiliary power relay 7 hasacted it breaks its own circuit and takes no more current. Relay Tisoi the same type asrelay 5. Such relays are well known in the art and for this reason the illustration of them in the drawing is exact details. r p

After the relay '7 has acted, the anodes of tubes 1 21 are open-circuited at the contact 22; the anode circuit of tube 23 is closed, beginning at coil 18, through coil 19 and conductor 54. The grid cir- The. grid circuit of tube 23 is closed throughconductor 54, contact 40, coil 42, and condenser 43 to ground. Resistance 45 becomesidle' The leak path for the grid of tube 23 is through the resistance 44, C011 46, a portion of resistance 35, conductor 34, and blade H to ground through the contact 33 on the transmit-receive switch.

By properly proportioning the resistances 44"- and 45 a suitable value of leak resistance will be 131 1 blade D moves off of the contact 16, since their jg'g only connection with the positive terminal of source Ea is through switch '36, conductor '55, blade D, contact 16, and conductor 56'. I 7

When the elementfi is moved to the left. a number of additional turns of the coils '19 and 42 are included in-circuit. I The resulting increased inductance of thesecoils is more suitablewhen only a single tube is operating." The coupling of these coils with the antenna is also changed. Y I I Telephony-low power 7 For transmitting at low power the switch .3 is moved to close contact 57, 'This causes to be included in the anode-cathode circuit of each tube 150 its L ssa-1'08 which is operating the resistance 5a This resisting key iz the resistance '69 is'shert-circuitedand ance is of such value that it cuts down the plate current to the desired value. No other change transmit with intermediate or high power the power switch is moved back to the appropriate position. When blade B passes to contact 14 the auxiliary power relay is caused to move to connect I equally available for transmitting either: buzzer modulated or continuous waves and is-properly' included incircuit without further action on. the I part of, the operator. than that of moving the all the tubes in circuit.

'Telegraphybuz zer modulatedi For transmitting continuous high frequency waves modulated at an audible frequency bymeans of the buzzer 11, the power switch -8 may be moved to any of the three available positions in the same manner as fortransmitting telephony. Instead of including the telephone circuit 1c in operative relation, the function switch 9 is moved to close the series of contacts 39, 59, 60 and 61.

When blade I is moved from the contact 39 effects no change in thecircuit. Closing the contacts59 and 61 energizes the buzzer 11 in the following manner; from ground,

through battery Ea, switchv 36 through conductors 3'7 and 62, resistance 63, thence. through two paths one of which extends through buzzer 11-, contact 59, blade G, and key 12 to ground through contact 33 on the transmit-receive switch. When this path is closed by the operation-of the key 12 the buzzer will be excited, thereby impressing its oscillations upon the amplifier Am through the transformers 47 and 48 by meansof the circuit through contact 61, blade I, conductor 64 and primary of transformer 47. to ground.

Continuous wave telegraphy Transmission of continuous waves at any of the three diiferent powers may. be'accomplished by moving the power switch to the appropriate position, thereby controlling the auxiliary power relay, these parts functioning in a manner similar to that hereinbefore described for telephony.

69 through conductor 34,'contact 66, blade G, and

key 12 to ground, through contact 33 on the transmit-receive switch.

When the key 12 is'openthe resistance 69 is included in the grid-leak circuit of the oscillator 0. By this means the resistance 69 is also included in the space current path of the tubes The grids of the oscillator tubes are connected to that terminal of resistance 69 which is negative, with respect to the grounded terminal, the latter being connected to the oscillator cathodes. A high negative potential is thus impressedhpon the grids. This negative potential is sufliciently high to reduce the space current to a small value or.

to zero with'the result'that the oscillations are caused to cease immediately after the; resistance 69 is included in circuit. Moreover, resistance 69, when included directly in the space current circuit, decreases the value of the space current, thus tending to prevent, oscillations- Upon closcontact 31 the' telephone circuit 10 is open-circuited. Closing When blade 'His moved tothe idle point from the point 30 theconductor 34- is opened:

and the key- 12 is :placed in the circuit 34,66, and- Blade I contacts-with the idle point 68 thereby open-circulating both the G- to ground at 32.

buzzerand telephonecircuits- The key 12 is thus functionswitchQto its appropriate position.

When transmitting telephony or buzzer moduerator to throw the transmit-receive switch from the transmitting to the'receiving position. when the oscillator Ois active. This-will tend to cause an arc to be drawn from contact 4 owing. tothe.

high potentials and large currents existing in the antenna. The shunt circuit around the resistance 69'to ground extends through the contact. 33 on the transmit-receive switch so that immediately when thetransmit-receive switch starts to move from the transmitting. position, thexresistance 69 will be included in the space currentpath as well v as in the leak path'of the oscillatori 1 i As above described, the oscillations will at once I cease when resistance 69 is included in the space: current path, since the grids of thexoscillatortubes are made highly negative because of the.

potential drop across the resistance 69. The generation of oscillations is checked so quickly'that,

by the time the switch is moved far enough to causean arc of appreciable magnitude, thedelivery of power. to the antenna by the oscillator will cease. The arcing action is, therefore, re-

duced to a minimum without the inclusionrof additionalapparatus other than the contact 33,

the resistance 69 serving to perform this addi? tional useful function.

The space current of the tubes always has.. its return path to-the negative side of. the source. Eb

through the resistance 35, one of the contacts 15. v

or 51 and the blade C. The conductor '70 leads from the blade C tothe grids of the; amplifying and modulatingtubesr Thecathodes are connectedthrough ground .to a more positive point.

on resistance 35. potential is thus impressed upon these grids. Y

Since the plate current varies with the number of tubes in circuit, the contacts 15 .and35l, lead ing to different points of the resistance 35, are

provided so that the proper potential difference between the grids and the cathodes of the tubes.

A suitable negative working i will result, irrespective of the. number of tubes, in operation. This adjustment is made whenthe' apparatus is constructed and'needs no attention onthe-part of the operator, the proper circuit i being closed automatically by movement of the power switch 8.

One form of the invention having .been' describedin detail, the novel features believed'to be inherent therein are defined in the appended claims. The invention is not to be regarded as tic:

limited otherwise than as indicated by the scope of the claims.

What is claimed is: c I 5 -1..In a radio system an oscillation generator comprising a plurality of associated elcctric dis jiquency waves Of power simultaneously controlled by said switch foreifecting changes in. the grid, anode and cathode circuits to permit the efficient operation of the device remaining activated.

a a 2. In a systemof space discharge devices having control, elements, a leak path for said elements, a. powercontrol switch for varyingthe number of said devices connected in. circuit, and means controlled by said switch ior'varying the, control element leak path in accordance with the number of said devices included in circuit.

3. In a transmission system, a signaling conductor; a system of thermionicidevice's connect- 4. In a transmission system, a power control switch having a plurality of positions and an auxiliary powercontrol switch having a less number of positions, means whereby said auxiliary switch one position of said control switch and another position for a plurality of other positions of said control switch,- and means whereby eachposition of said control switch transmits high freposition.

5; In a transmission system, a plurality of electric discharge devices, a power control switch having one position corresponding to a circuit f rent path connected in shunt to said resistance condition for operating one number of said devices, and a plurality of other positions corresponding to a circuit condition for operating'an other number of said devices, means operated by a change from one to another of said other positions to change the circuit of said devices with power'level different from that at another posi- 1 tion. I

6. In a transmission system, a powerdevice, an

additional power device each of said'devic'es havingan anode-cathode circuit, a grid leak circuit and a cathode'circuit, and means for controlling said devices comprising a member for controlling said anode cathode circuits, a second member for controlling the connection between said power device and said additional power device, a third member for controlling the grid leak circuit ofsaid power device,and a fourth member for controlling the energization of the cathode circuit of said additional power device.

-:'7. In a transmission system, power radiating means. a plurality of electric discharge devices for a plurality of power levels and to simultaneously control the operation of said auxiliary switch to adjust the power radiating means for operation at the. respective power levels.

8., Ina transmission system, a source .of carrier waves, abuzzer, a modulating device, a tele graph key and a functionswitch, said function.

switch beingassociated with means whereby .in one position it connects said buzzer with said source through said modulating device whereby said waves-may be modulated in accordance with is automatically made to assume one position for 7.

different from any other changed number of devices.

a code. by said key, and =inanotherpositionsaid waves may beinterruptedinaccordance with a 10.,A space discharge tube, appropriatecircuits connected thereto for the generation of oscillations,,a work circuit, a switch for connecting,

and disconnecting said work circuit to and from said generator, a control element in said generator, a control path connected to said element, and 'means controlled by and operated at the initiation of the disconnecting movement of said switch for affecting said path in a manner to cause cessation of generating'action.

11.-IncombinaL-ion, an antenna, a signal receiving, circuit. and a signal transmitting circuit,-;

and a switchfor alternately connecting. the receivingand transmitting circuits to said antenna, W

said signal transmitting circuit comprising a signaling element, a thermionic device having a control circuit, aresistance element insaid con-' trol circuit, a current path connected in shunt to said resistance element when said switch is in the transmitting position, and an alternative curby the operation of said signaling element.

12-. In'a vacuum tube system, a vacuum tube having an anode, a cathode and a grid, asource of anode-cathode current, a ground connection for the cathode, a ground connection for the negative terminal of the source of anode-cathode current, an element having a high resistance, and

signal means for'eiiectively' connecting. and dis'-' connectingv the high resistance. element in the ground connectionof the negative terminal of the anode-cathode current source.

13. Ina'space discharge'system, a plurality of discharge devices having control elements, a source of polarizing potential for said control elements, a control means for varying the number of said .control' elements included in circuit', and meansoperated thereby upon changing the number of said devices to change said source, to

a condition suitable for operating with the 14. In a space discharge system, a plurality of discharge devices, a current. path therefor, a

I plurality of devices whose. grid potentials are derived from said current, path, control meansfor changing the number of said devices connected in operative relation, and means controlled by said controlmeans for varying the grid polarizing action of said path.

15. In combination, an antenna, aradio receiving circuit, a radio; transmitting circuit com prising ,a thermionicdevice having a control ele- 'ment, a transmit-receive switch for alternately 16. In a radio system, an antenna, a receiving circuit, atransmittingcircuit a transmit-receive switch for alternately connecting said antenna to the receiving and transmitting-circuits, an

electric discharge :devicein :sai'd transmitting circuit, said device having a cathode, an anode and a control element, an anode-cathode circuit for said device, a resistance element, connections from said resistance element to saidcontrolelement, and means controlled bysaid transmit-receive switch for connecting said'resistanceelement in said anode-cathode circuit. 1 i

17. In a signaling system a'space discharge device connected to a transmission circuit for the transfer of energy thereto/a signaling circuit closing device, a resistance, a control elementin said discharge device connected. to a point on said resistance, a space current sourcef'means controlled by said circuitclosing device tocause said source to establish saidpoint at asufiici'ently high negative potential tostop the transfer of energy to said transmission circuit. I 18. A space discharge device, appropriate circuits connected thereto whereby said device generates oscillations, a resistance, .a; control element in said device, a space current circuit for said device, connections for including said resistance insaid space current circuit whereby said conn01 element is negatively charged, and means for closinga path. in shunt to said resistance.

19. A space discharge device, including a control element, a space current circuit for said device, a control element circuit for said device, a resistance, means for including said resistance in the space current and. control element circuits of said device whereby said: control element is made more negative and the external resistance of said space current circuit is increased, and signal transmitting means for closinga path in shunt to 'said'resistance p I 20. In a vacuumitube transmission system comconnection from the grid to the' terminal of said resistance which' is electrically adjacent the negative terminal of said current supply source, said resistance being short circuitediwhen said: system isoperating; and means'for connecting said'resist- 3211106, in: circuit to renders'aid system inoperative.

421. In a vacuum tube'system, a grid-filament circuit, an anode-filament circuit, a resistance common to said circuitsand a signaling element "for closing a'circuit of low impedance around said resistancerduri'ng signaling periods.

22QA discharge device having an anode, a cathode and acontrol grid, a grid-cathode circuit, a cathode-anodecircuit coupled to said gridcathode circuit, and a resistance in said cathodeanode. circuit and said grid-cathode circuit, said resistance being of's'uch value that the'normal anode-cathode current necessary to permit the ge'nerationof oscillations if the grid were normally polarized, produces such a valueof negative grid potential as to prevent the generationof oscillations. A 1 i i 23'. A' spacedischarge device having a cathode, an anode, and a grid or control electrode, a gridcathode circuit, a cathode-anode circuit, a space cluding. asource oi. potential, which" method-cornelectrodes, a'circuit connecting sai 'audi'ons with said antenna earthsystem'.'-

prises producing a negative'potential from the normal flow of current inthe space current-circuit,-impressing thatnegative potential upon the con-trolelement to reduce and tend to blockjthe flow of space current, producing from the reduced flow of space currenta stable negative potential, and impressing the stable negative potential on the control element to maintainthe flow of space currentat a low value.

. 25. A radio signaling system comprising an 'antenna earth system, a plurality of "audionsh'aving plate, grid and filament electrodesdissociated- -therewith, ac'ircuit connecting saidplate eleca trodes to each other andto said filamcnt electrodes, a circuit connecting'said grid electrodes'jto each other, a circuitccnnected between' said 'grid electrodes" and said filament electrodes and-ineluding therein aresistance', and means for varying said resistance by and in signals. v

26. A radio signaling system comprising an antenna earth system, a plurality of audions havingplate, grid and filament electrodes 'asso'- ciated therewith, a "circuitconnectingsaid" plate electrodes to each other and to said filament electrodes, a circuit connecting said grid electrodes to each fother,-a circuit connected 'be-- tween said grid electrodes and said' filament electrodes and including thereinya resistance, and means for varying said resistance by and in accordance" with ,signalsg and means for associatmg said audionsiwith said antenna earth-system.

'27. A radio signaling. system comprising an accordance with antenna earth system, a plurality of audions having plate, grid and: filament electrodesassm ciated therewith, a circuit connecting said plate electrodes to each 'otherf and tosai-d filament 28. A radio signaling system'comprisingfan antenna earth 'sys tem-,\a plurality of audions having plate, grid and filament electrodes 'as'sociated therewith, ajcircui-t connecting said plate electrodes to each'o'ther and" to said filament elecgrid electrodes, a circuit connecting said grid electrodes to each other, a circuit connected; between said grid electrodes and said filament electrodes] and including therein a resistance; and means for varyingsaid resistance by and in "accordance with signals, and means included in said plate and grid circuits for'associating' said audions with said antenna earth system and with "each other.

29. The method of operating an electron discuit connections connected theretof for the production of high frequency oscillationswhi'c'hconsists in supplying current thereto through a re- I sistance device, varying the value of "the resist ance of said device between a low anda .comparatively high value, and simultaneously p'ro-.

ducing a high negative potential on the grid of the electron discharge device. Y

30. In combination a thermionic "oscillation generator and a thermionic modulator having their plates connected in parallel, and means, including a resistor in the plate circuit of said d t r, for controlling the'gr'id potential in 5 t e g nerator,

supplied to said anode to said cathode,,a second circuit exterior to the tube from said control electrode to said cathode, a ground connection for said cathode, a'

second inductor coupled to said first-named inductor,*a second condenser serially connected with i said second inductor in said anode circuit, a third condenser in shuntto saidsecond inductor, a

third inductor coupled to said first-named in- P prising-an antenna ground system, an electron ductor and connected in said control electrode circuit, a fourth condenser in series therewith in said circuit, a resistor in shunt to said fourth condenser, and means for varying the electrical constants of the circuit thus constituted, substantially as described. 32. An, electric discharge device for generating oscillations, said device having a cathode, an anode and a control element, a cathode-anode circuit forsaid device, a resistance element connected in said cathode-anode circuit, 'a connection from said resistance element for applying a negative potential to said control element, and a key. for controlling the negative potential control element by said resistance.

' 33. In a wave transmitter, a signaling conductor, a high frequency circuit, a system of'electric discharge devices connected to said conductor by means of said circuit, means for producing in said systemof electric discharge devices a plurality of waves ofdiiferent wave forms, a function switch for selecting that one of said means for producing the desired wave to be transmitted, apower switch'for controlling the number of said devices connected to said circuit with whatever wave form is atany time selected by said funcspace current circuit, and means for opening and closing a path inshunt to said resistance.

35, In combination, anantenna,a radio receiving circuit, a radio transmitting circuit comprising an electric discharge device having a cathode and a control element, switching means for alternately'connecting said receiving and transmitting circuits tosaid antenna, and means 0perativewhen said switching means is operated to.

connect the antenna to the receiving circuit for impressing a negative potential on said control element.

36. In combination, an antenna, a radio receiv- .er,;a radio transmitter, a switch for alternately connecting said antenna to said receiver and.

transmitter, an electric discharge device for said transmitter, an anode-cathode circuit forsaid device, a source of. current, connections for supplying current from said source to said anodecathode. circuit, a resistance element, and means controlled by said switch for including said rewsistance element .in said anode-cathode circuit when said antenna is connected to said receiver and for effectively disconnecting said resistance ,lecting or radiating circuit from said anode-cathode circuit when said an} tenna is connected to said transmitter.

, -37..In combination, an antennaga radiore- 'ceiver, a radio transmitter including an electric discharge device circuit for producing waves ofamplitude suitable for radiation, means :for alternately. connecting said antenna to said receiver. or said transmitter, and means controlled by the alternately connecting means for reduclower than said amplitude-suitable forradiation and greater than zerowhen said antenna is connected to said receiver.- w i 38.. A transmission and receiving system'comtube oscillator, a radio receiving circuit including an electron tube detector andza responsive device, switching mechanism for alternately es- 'tive simultaneously with the actuation of said switching mechanism for changing the amplitude of the oscillations developed by said oscillator when said oscillator is connected in circuit with said antenna ground system or when said antenna ground system isconnected with said re-. ceiving circuit. 39. A transmission and receiving system comprising a radio frequency energy transmitting and collecting circuit, a transmitter including an electron tube oscillator having aninput circuit and an output circuit, means'for limiting the amplitude of the oscillations developed :by said electron tube oscillator, a radio receiving system, and means for alternately establishing connection between said radio frequency energy collecting; or radiating circuit :and said'oscillato'r and said receiving circuit, said means operating,

to simultaneously control said aforementioned 1 means for reducing the'amplitude' of oscillations developed by said oscillator when said radiofre-f quency energy collecting orradiating circuit is connected with said receiving circuit. f

tem comprising a radiofrequency energy collecting .or radiating. circuit, anelectron tube. system having inputandi output circuits arrangedrfor the production of high frequency oscillations, a

resistor arranged in the output circuit fofwsaid electron tube system, a signal receivingwcircuit,

ing the amplitude of said wavesto an amplitude means for alternately establishing connections between .said radio frequency energy collecting or radiating circuit, said oscillator and said receiving circuit, said means operatingto shunt said i resistor when said radio frequency en'ergy col is connected with said oscillator. v

41. In a high frequency signaling system employing an electron discharge device having i an.anode,.a cathode and a grid, a source of po-' tential for said anode, a resistance permanently connected between said grid and the negative side-of said source of potential, a connection between said cathode and the negative side ofsaid 1 source of potential, means for controlling the operation of said electron discharge device com- A. do

prising a contact making key inserted in said last f mentioned connection,,one side of said key be ing connected both to the negative side of said 7 source of potential andto said grid, and the other side of said key being connected to the .cathode,; and a-parallel combination of. resistance and capacitance connected in parallel with said key.

d2, In a high frequencysignaling systemiem- F.

'40. Asignal transmissionrand reception sysmentioned connection, one side of said key be-' ving connected to the negative side of said source of potential and to said grid, and the other side of said key being connected to'the cathode, and means associated therewith and adapted to maintain a definite negative potential on said grids and across said key when said key is open, said means comprising a parallel combination of capacitance and resistance connected in parallel with said key. w

LEWIS M. CLEMENT. 

